I personally wouldn't use the ZxR with a Game Zero, it has a horrendously high output impedance (38 ohms) and Senns are susceptible to low damping ratios - it should be at least 8:1 whereas this would be 50:38, which would likely result in overblown, flabby bass due to poor control of the voice coils.
Bass increase comes from Sennheisers having horribly bumpy impedance curve with impedance literally multiplying couple times at driver's resonant frequency:
http://graphs.headphone.com/index.p...e=30&graphType=7&buttonSelection=Update+Graph
With output impedance that forms frequency dependant voltage divider...
Resulting bigger part of output's power driving headphone at those frequencies.
For flat impedance curve cans output impedance just lowers damping factor.
Inline volume controls or those in for example Game One and Zero headsets work same way as output impedance.
As above; and also, for gaming, the increase in cost is not worth it. ZxR would only make sense if you were using headphones for gaming that needed more power than the SB Z can give.
ZxR needs both pwoer and voltage hugnry cans for it to work.
For just power hungry low impedance cans that output impedance wouldn't be good.
Anyway new AE-5 is both lot cheaper and has better headphone output than ZxR.
Creative isn't only one with output impedance problems.
One Asus Xonar serie had even 100 ohm output impedance.
Asus Strix Raid Pro seem to have same "feature":
http://reference-audio-analyzer.pro/en/report/amp/asus-strix-raid-pro.php#rw3